Process for the cold reduction of strip metal



United States Patent THE COLD REDUCTION OF srmr METAL No Drawing. FiledJuly 25, 1958, Ser. No. 750,849

5 Claims. (Cl. 29424) PROCESS FOR This invention relates to improvementsin the process for cold reduction of strip metal. In particular, itrelates to a method for improving lubrication of pickled metal strip atthe end of the pickling line just prior to recoiling and cold rolling.It also relates to a method for improving lubrication on the mill duringthe cold reducing process. Although this invention is applicable to thecold reduction of all metals, both ferrous andnonferrous, it is ofparticular utility in the cold reduction of steel.

It is an object of the present invention to eliminate friction scratchesoriginating at the recoiler. It is a further object of this invention toobtain good shape of the strip during the process of cold reduction bymeans of improved lubrication; In particular, it is an object of thepresent invention to provide a method for operating cold reducing mills,specifically steel mills, at higher speeds because of improvedlubrication between the strip and the rolls. Other objects of thisinvention will be apparent as hereinafter set forth. I It is well knownthat modern cold mill construction permits the attainment of speeds upto and in excess of 5000 feet per minute on the delivery end of themill. In some cases, new mills are rated as high as 6500 feet perminute. In spite of these high ratings, however, it has been foundimpossible to operate these mills at such speeds because of inadequatelubrication of the strip as it passes betweenthe reducing rolls. It isparticularly desirable to attain the highest possible speeds in order toinsure maximum output when rolling blackplate or tinplate, i.e. stripranging in final thickness down to about in the order of 0.008 inch.Palm oil is the material most commonly employed as lubricant in currentindustrial-practice for rolling tinplate gauges, but with this materialit is not practicable to attain speeds much in excess of 4000 feetperminute for any length of time even on mills rated at much higher speeds.Overload or friction scratches, poor shape, breaks, and other troubleswell known to steel mills occur when higher speeds are attempted withpalm oil or with any other rolling lubricant which has been used upuntil the present invention.

We have now found that speeds varying from several hundred to over athousand feet per minute greater than those obtainable with palm oil canbe attained and main- ,tained over protracted periods by. utilizing asrolling. lubricant, otherwise known as rolling oil, processed fats andfatty oils or mixtures thereof of animal or vegetable in the case ofoils which do not gel under such prolonged conditions of heating. Itwill normally not be less than six hours. I

In general, we may use any fat or fatty oil of animal 'or vegetableorigin comprising essentially non-drying or semi-drying'components. Weprefer to use fats or oils which are largely saturated or mono-olefinicin the structure of their component fatty acids, in particular thosefats and oils which are edible such, for example, as lard, hydrogenatedfats and oils like Criscoa product manufactured by Procter and GambleCompany, corn oil, peanut oil, or blends of cottonseed and corn oilwhich may or may not be hydrogenated such, for example, as thatavailable under the trademark Yolanda (CIF. Simonins Co., Inc., Phila.,Pa.). We prefer to use fatty, semi-solid heat processed edible fats,oils, and greases which may or may not be reclaimed. We may however, useany heat-processed fat or oil of non-drying or semidrying nature.Reclamation will usually consist essentially of melting if necessary,straining and/or settling insoluble solid matter in such manner that thefatty material is freed of extraneous non-fatty solid material andsubstantially freed of moisture. The reclamation process may be carriedout simply by blending available melted fats, oils and greases andstraining the blend through grates or perforated plates, thentransferring to settling vats where it is further heated to establishhomogeneity and drive off water before collection in storage tanks.Reclamation may also be carried out by treatment with live steam,filtration, and settling. Other procedures may be employed for the samepurpose and the final product may, if desired, be washed with brine oralum solution in order to clarify it and aid in removal of water. Suchreclamation processes are well known to the fat rendering industry. Inall cases, the fat, oil or grease reclaimed will have been heatprocessedas hereinbefore stated prior to reclamation.

Although the chemical literature is replete with the results oftheoretical investigations which have been undertaken to learn thenature of chemical reactions which occur during the heat treatment ofvarious fats and oils, we are not able to identify the remarkableimprovements in rolling properties effected by this heat treatment withany specific chemical changes. One of the most apparent physical changesoccurringduring this processing is the increase of viscosity. Thus,samples of eight different types of fats, oils, and greases weresubjected to heat in a stainless steel beaker at 300 F. to 350 F. for 24hours. Samples were removed at the end of 12 hours and 24 hours, andcompared in viscosity with the original products before heating with theresults given in the following table:

Viscosity of heated fats and oils at F.

'(Saybolt Universal seconds) While a considerable degree of latitude ispermissible in the viscosity of heat-processed oils used according toour present invention, it will generally run between from about 200 toabout 500 Saybolt Universal seconds at.

100 F., the preferred range being 230 to 320. Although useful productsmay be liquid at room temperature, we prefer to employ heat-processedfats, oils, and greases having a pour-point ranging from about F. toabout 85 F., preferably from 55 F. to 50 F.

When examined for frictional properties by means of the Falex machine(U.S. Patents 2,106,170 and 2,110,- 2 88) modified so as to measuretorque in gram centimeters, using a lever approximately 20. inches inlength, a representative sample of heat-processed fat having an acidnumber of 12, a saponification number of 200, and a titre of 40 C.,showed a torque of 10,150;gram-centimeters. In contrast to this value, atypical sample of palm oil tested at the same time gave a torque of12,600 gramcentimeters, i.e., a value 24% greater.

The rolling oil used in accordance with the process of this invention,i.e., heat-processed fatty oil or grease, may be applied to the coldreduction of steel according to any of the well-known current steel millpractices in place of palm oil or its equivalent. Thus, it may be usedin the so-called direct application method or, in conjunction with anemulsifier, if desired, in recirculating systems. It may be used oneither single stand or tandem mills, or on reversing mills.

In a typical run on a five stand tandem mill, the rolling oil of thisinvention was stored in storage tanks at 150 F. and mixed with Water atthe same temperature by means of proportioning pumps through which itwas fed and supplied to the mill rolls. It was used at a ratio of aboutone part of oil to ten parts of water in, the first three stands and ata ratio of about one part of oil to eight parts of water at the last twostands. This corresponds to average mill practice although, at. times,the ratio of premixed water and rolling oil may run between theapproximate extreme limits of 1:1 and 20:1. The strip was cooled in thecustomary manner while passing through the mill by flooding with water.The hot rolled band to be cold reduced was coated at the pickler oilerwith the same oil of this invention and coiled befo're being fed throughthe tandem mill. Band rangingin initial gauge from 0.079 to 0.082 inchin thickness was reduced to a finished gauge ranging from 0.0083 to0.0098 inch.

Approximately 500,000 lbs. of steel was cold reduced in this run, withspeeds of 5500 feet per minute being attained. In general, in order tomaintain friction scratches at a minimum, it was found advisable tooperate at 5000 feet per minute which speed was maintained continuouslyduring several hours. These speeds were several hundred feet per minutefaster than could be attained with palm oil on the same mill. Reductionon the mill was excellent, as was surface appearance and shape. Thesheet so produced was subsequently annealed, cleaned, and tinned-half byelectrolytic tinning, half by hot dipping, using conventional methods.The tinplate thus produced was of prime quality. In another run on thesame mill, carried out in a manner similar to that just described, fortycoils of steel having a tinplate gauge of 0.0087 inch was reduced fromhot band of 0.080 inch thickness at a speed of 4500 feet per minute.This speed compares with a maximum speed previously obtainable with palmoil on the same mill, with the same steel and similar reductions, of3500 feet per minute.

it is thus evident that the process of our invention, utilizingheat-processed non-drying and semi-drying fats, oils, and greases as acoating oil for application at the "pickler oiler and as a rolling oilon the cold reduction mill atfo'rds a means of efiecting substantialeconomies in the manufacture of strip steel.

It is to be understood that the essential lubricant of this invention,i.e. heat-processed fats and fatty oils of non-drying or semi-dryingnature, may, if desired, be compounded with other materials 'known tothe lubricating art, such as other fats and fatty oils which have notbeen heat-processed, mineral oils, extreme pressure additivesemulsifying agents and the like.

We claim:

1. In a process of cold reduction of strip metal, the step whichcomprises coating the metal prior to passing. same between reducingrolls with a rolling oil containing a lubricant selected from the groupconsisting of fats, oils and greases of non-drying and semi-dryingcharacteristics heat treated at a temperature ranging from about 200 F.to about 500 F. from about 6 to about 72 hours and having a viscosity offrom about 200 to about 500 Saybolt Universal seconds at 100 F. and apour point from about 0 F. to about 85 F., said lubricant being stableat high cold metal reduction speeds.

2. In a process of cold reductio'n of strip metal, the step whichcomprises coating the metal prior to passing same between reducing rollswith a rolling oil containing a lubricant selected from the groupconsisting of fats, oils and greases of non-drying and semi-dryingcharacteristics heat treated at a temperature ranging from 250 F. to 450F. from about 6 to about 72 hours and having a viscosity of from about200 to about 500 Saybolt Universal seconds at 100 F. and a pour pointfrom about 0 F. to about 85 F., said lubricant being stable at high coldmetal reduction speeds.

3. In a process of cold reduction of strip metal, the step whichcomprises coating the metal prior to passing same between reducing rollswith a rolling oil containing a lubricant selected from the groupconsisting of fats, oils and greases of non-drying and semi-dryingcharacteristics heat treated at a temperature ranging from 300 F. to 350F. from about 6 to about 72 hours and havinga viscosity of from about200 to about 500 Saybolt Universal seconds at 100 F. and a pour pointfrom about 0 E. to about 85 F., said lubricant being stable at high coldmetal reduction speeds.

4. In a process of cold reductio'n of strip metal, the step whichcomprises coating the metal prior to passing same between reducing rollswith a rolling oil containing a lubricant selected from the groupconsisting of fats, oils and greases of non-drying and semi-dryingcharacteristics heat treated at a temperature ranging from 300 F. to 350F. and having a viscosity of from about 200 to about 500 SayboltUniversal seconds at 100 F. and a pour point from 50 F. to F.

5. In a process of cold reduction of strip metal, the step whichcomprises coating the metal prior to passing same between reducing rollswith a rolling oil containing a lubricant selected from the groupconsisting of fats, oils and greases of non-drying and semi-dryingcharacteristics heat treated at a temperature ranging from 300. F. to350 F. and having a viscosity of from 230 to 320 Saybolt Universalseconds at F. and a pour point from 50 F. to 70 F.

References Cited in the file of this patent UNITED STATES PATENTS2,383,906 Zimmer Aug. 28, 1946 2,413,121 Swenson Dec. 24, 1946 2,486,130Dietrich Oct.- 25, 1949 2,588,625 Ferner, Mar. 11, 1952 2,590,451 Perry2 Mar. 25, I952 UNITED STATES, PATENT OFFICE GERTIFICATE or CORRECTIONPatent No, 2,938 262 May 31, 1960 t George E. Barker et alu It is herebycertified that error appears in the printed specification of the abovenumber-ed patent. requiring correction and that the. said Letters Patentshould read as corrected belowa Column 4 lines 50 and 59 after "70 F3,each occurrence,

insert said lubricant being stable at highcold metal reduction speedsSigned and sealed this 22nd day of November 1960.

(SEAL) Attest:

KARL H, AXLINE ROBERT c. WATSON, Attesting Officer I Conmissioner ofPatents

1. IN A PROCESS OF COLD REDUCTION OF STRIP METAL, THE STEP, WHICHCOMPRISES COATING THE METAL PRIOR TO PASSING SAME BETWEEN REDUCING ROLLSWITH A ROLLING OIL CONTAINING A LUBRICANT SELECTED FROM THE GROUPCONSISTING OF FATS, OILS AND GREASES OF NON-DRYING AND SEMI-DRYINGCHARACTERISTICS HEAT TREATED AT A TEMPERATURE RANGING FROM ABOUT 200*F.TO ABOUT 500*F. FROM ABOUT 6 TO ABOUT 72 HOURS AND HAVING A VISCOSITY OFFROM ABOUT 200 TO ABOUT 500 SAYBOLT UNIVERSAL SECONDS AT 100*F. AND APOUR POINT FROM ABOUT 0*F. TO ABOUT 85*F., SAID LUBRICANT BEING STABLEAT HIGH COLD METAL REDUCTION SPEEDS.